1. Field of the Invention
The invention is directed to an aluminum electrolytic capacitor that comprises a capacitor winding, an anode foil provided with a dielectrically effective barrier layer having a spacer (particularly of paper saturated with operating electrolytic), and a cathode foil, and that is built into a housing.
2. Background of the Invention
These types of capacitors are initially wound dry, and the capacitor winding is subsequently impregnated with the operating electrolytic in a bath. The electrolytic penetrates into the inside of the capacitor via the two end faces of the winding. The region that is impregnated last in the winding (usually the middle winding region) is impregnated poorest, particularly when impregnating capacitor windings with large diameters, for example, electrolytic capacitors whose cup housing comprises a screw connection, . The development of gas connected with it has a negative influence on the use duration of the capacitor.
In order to eliminate this problem, the impregnation temperatures can be lowered, for example. However, this increases the impregnation time, thus requiring an expensive investment.
An improvement of the impregnation quality can also be achieved by utilizing papers with a lower density. In order to achieve an adequate dielectric strength, however, these papers must be thicker, resulting in the dimensions of the capacitor winding often becoming too big.
There are also impregnation papers in the marketplace having the name PDHX that have been available since about the end of the 1980""s and that are shaped like a corrugated sheet (i.e., repeat patterning). A 50 xcexcm paper having a density of 0.6 g/cm3 is formed from a 40 xcexcm paper having a density of 0.75 g/cm3. Since, however, this paper is elastic, problems arise when cutting or in the re-reeling connected with it. Moreover, an improvement of the impregnation can only be achieved with this paper under specific impregnation conditions.
The described problems do not arise given vacuum impregnation of very small electrolytic capacitors (winding length  less than 20 mm).
An object of the present invention is to provide an electrolytic capacitor in which impregnation conditions similar to those in small electrolytic capacitors can also be produced in a large capacitor winding and in which the winding impregnation is improved without lengthening the impregnation time.
This object is inventively achieved in that the spacers have an impressed line structure that is arranged from one end face of the capacitor winding to the opposite end face.
Advantageous developments of the invention are explained in greater detail below with reference to exemplary embodiments.